The present invention relates to pumps for discharging water from washing machines or the like and, in particular, to a high efficiency pump resistant to clogging from wastewater debris.
Clothes washing machines employ a pump for draining washwater from a washtub after completion of a washing cycle. The washwater typically includes suspended dirt and lint from the wash, as coarsely filtered through holes in a spin basket held within the washtub. The washwater may also include larger items, such as buttons or coins, and small articles of clothing, such as handkerchiefs and shoelaces, which may find their way around the edge of the spin basket into the washtub or even through the relatively large holes in the spin basket. Such debris in the washwater may clog the pump used to drain the washtub.
A screen placed directly between the pump and the washtub to protect the pump would be expected to clog frequently from an accumulation of lint. Accordingly, the coarse filtering of the spin basket alone is relied upon and the clearance of the pump impeller and housing is increased so as to reduce the chance that a hard and compact item such as a button will become jammed between these moving surfaces. The increased clearance between the impeller and housing lowers the efficiency of the pump thereby increasing the cost of operation. Further, even high clearance pumps are susceptible to fouling by items such as shoelaces or strings which can wrap about the impeller despite the increased clearance.
The problem of pump clogging can be more acute in high water conserving washing machines where smaller pumps and lower amounts of water are used.
The need exists, therefore, for a high efficiency washwater pump resistant to clogging from washwater debris.